Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

39 Wireless charging | Focus field of 10 kW across a ‘power cloud’ which is 10 m in diameter and which can charge a number of UAVs. A receiver for the system will be demonstrated at the CES show in Las Vegas in January 2019. One application is autonomous charging in remote areas where the UAV doesn’t have to deal with obstacles on take-off and landing, and hovering is a simpler, more reliable control algorithm. This far-field system can also be used for warehouse applications, for monitoring inventory or for security. Because there is no need for a landing pad, the transmitter can be mounted on the roof or even the side of a building to create the power cloud. The system’s developer is aiming to build a network of such transmitters in a mesh three to five miles apart so that a UAV can travel any distance, charging up as it flies. For a powerline monitoring application, for example, a transmitter could be installed every 15 miles. The ultimate intention is to scale up the transmitter to 100 kW in 2020 to power UAVs that carry passengers, such as the Ehang or Volocopter platforms, and use the mesh to provide power to autonomous flying taxis. The system is based on a resonant capacitive circuit operating at between 100 and 150 kHz with variable inductance at a very precise, stable frequency. The transmitter is made from 2000 copper- plated aluminium wires in a loop, which can be any shape. The shape determines the inductance of the resonant circuit and would vary with the installation. That shape then determines the base frequency of the transmitter, so it can be complex to set up initially. A 2.4 GHz radio channel links the transmitter with multiple receivers. It provides data to tune the resonant circuit in the receiver on the UAV, and as more UAVs enter the power cloud to charge, the resonant frequency changes so that they can all be charged while in flight. The power delivery in the UAV is handled by a module that weighs 200- 300 g and has the latest wide bandgap conversion devices to provide synchronous rectification at 100 kHz of a 500 V input down to 48 V at 99% efficiency for charging the battery pack. The end-to-end efficiency at a distance of several metres has not yet been disclosed. Ground vehicles A wireless fast-charging technology is being rolled out on a test fleet of Kia cars in the US. The three-year project resulted in a compact wireless charging system that can transfer more than 10 kW with 85% grid-to-vehicle efficiency. The system has been tested in real- world applications for durability, safety and performance. It uses a proprietary near-field power system with magnetic inductive coupling. Overlapping coils allow for high current transfer and a degree of misalignment between the transmitter and the receiver, making it easier for day-to-day use. BMW has also started to roll out wireless charging using magnetic inductive charging. The hardware consists of a charging station, called a GroundPad, installed in a garage or outdoors, with a receiver, called a CarPad, mounted on the vehicle underbody and connected to the battery management system. The system operates at a distance of 8 cm and delivers 3.2 kW with an end-to-end efficiency of 85%, allowing a BMW 530e iPerformance to be fully charged in about three-and-a-half hours. Researchers and start-ups around the world have been working on capacitive approaches to wireless power. A team in Colorado for example is looking at a novel megahertz frequency capacitive system for electric vehicles that safely operates within the ISM spectrum at around 2.4 GHz. This would transfer 1 kW across a 12 cm air gap with an efficiency of more than 90% and a power density of 50 kW/m 2 – twice that of current methods. Materials Embedding metal coils in miles and miles of road is not a practical proposition, but a German start-up has developed a technique to add metallic particles into concrete to develop a ‘magnetic road’. The concrete consists of 87% magnetisable aggregates, which are a waste product derived from the manufacturing of ceramic ferrites and the recycling of electronic scrap. It is being tested out in Salo in Finland, Changzhou in China, and in the German capital, Berlin. Unmanned Systems Technology | December/January 2019 A low-cost combined wireless charging/landing platform is being tested to support inspections of telecoms lines (Courtesy of Divisek)